Lubrication system for gas turbine engines

ABSTRACT

A lubrication system is disclosed. The lubrication system may be used in conjunction with a gas turbine engine for generating power or lift. The lubrication system utilized a flow scheduling valve which reduces lubricant flow to at least one component based on an engine load. The lubrication system may further include a main pump which may be regulated by an engine speed. Thus, a lubrication system which provides a lubricant to engine components based on the load and speed of the engine is possible. The system may improve efficiency of the engine by reducing the power previously spent in churning excess lubricant by at least one engine component as well as reducing the energy used by a lubricant cooler in cooling the excess lubricant. The lubricant cooler size may also be minimized to reduce weight and air drag due to the reduced lubricant flow.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/690,767 filed on Nov. 20, 2012, the disclosure of which isincorporated by reference herein in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to gas turbine engines and,more specifically, to the lubrication systems of gas turbine engines.

BACKGROUND OF THE DISCLOSURE

Gas turbine engines of modem aircraft require a supply of oil tomechanical components such as, but not limited to, bearings, seals, andthe like. The oil can be used as a lubricant, a coolant, or both forthese components. Typical oil systems supply the oil to a manifold whichthen directs the oil to different engine components. In some systems,the oil then progresses to a tank for holding the oil before it ispumped back to the components to lubricate them again. In other systems,the oil is simply pumped back to the engine components and stored in asump at each component. When the oil leaves the tank it is filtered toremove unwanted debris and de-aerated to remove any air absorbed by theoil while lubricating and cooling the components. An oil cooler alsoremoves additional heat gained from the lubricated components. Commonly,the fuel for the engine is used as the coolant, as the fuel movesquickly in relation to the oil allowing the fuel to absorb a largeamount of heat from the oil. Other lubrication systems may have thefilter, de-aerator, or cooler arranged in the system such that the oilinteracts with these components after leaving the engine components butbefore returning to the tank or sump.

In prior art oil systems, the quantity of oil pumped to the componentsis typically based on a high speed and high load condition, or isregulated based on the speed of the engine. However, either approachoften results in an oversupply of oil, at least in low load conditions,such as during cruise or a high altitude climb, for example. Thisreduces the efficiency of the engine in that the excess oil is churnedby the engine component, imparting extra heat to the lubricant. Thislubricant then needs to be cooled before being used as a coolant orlubricant for the engine components again and thereby drawing power fromthe engine. Additionally, the bulky coolers needed for cooling the oilincrease the weight of the engine, and in turn weight of the aircraft,thereby reducing fuel economy. In light of the foregoing, it can be seenthat an oil system is needed that can provide oil in the quantity neededunder the specific load and speed conditions the engine is experiencing.

SUMMARY OF THE DISCLOSURE

In accordance with one aspect of the disclosure, a lubrication systemfor a gas turbine engine is disclosed. The lubrication system mayinclude a main pump which may move a lubricant through a main conduitfrom a lubricant tank to an engine component. The system may furtherinclude a flow scheduling valve positioned in the main conduit betweenthe main pump and the engine component. The flow scheduling valve maylimit lubricant flow to the engine component based on a calculated loadof the gas turbine engine and redirect excess lubricant through a returnconduit to the lubricant tank.

In a refinement, the lubrication system may further include a lubricantcooler connected to the main conduit.

In a further refinement, the cooler may be positioned between the mainpump and the engine component.

In another refinement, the lubrication system may further include afixed flow metering orifice positioned in the main conduit between themain pump and the engine component. The metering orifice may allowlubricant to bypass the engine component via a bypass conduit and returnto the lubricant tank.

In another refinement, the engine load is calculated by a processor froma combustor pressure.

In yet another refinement, the engine load is calculated by a processorfrom a fan speed measured by a speed sensor.

In yet another refinement, the main pump may be regulated by an enginespeed.

In yet another refinement, the lubrication system may further include amanifold positioned in the main conduit between the main pump and theflow scheduling valve. The manifold may be connected to the enginecomponent via a side conduit. The side conduit may allow the enginecomponent to receive lubricant flow not reduced by the flow schedulingvalve.

In accordance with another aspect of the disclosure, a gas turbineengine is disclosed. The gas turbine engine may have an engine componentrequiring lubrication and further include a compressor, a combustor, aturbine, a lubrication tank, a main conduit, and a flow scheduling valvepositioned in a main conduit between the lubricant tank and the enginecomponent. The valve may limit a flow of lubricant from the lubricanttank to the engine component based on a load on the engine component.The valve may also redirect excess lubricant through a return conduit tothe lubricant tank.

In a refinement, the lubrication system may further include a main pumpconnected to the main conduit. The main pump may pump lubricant from thelubricant tank to the engine component.

In a further refinement, the main pump may be driven by a drivetrainmechanically connected to an engine rotor.

In another refinement, the load on the engine component may becalculated by a processor based on a parameter measured by a pressuresensor and/or speed sensor.

In another refinement, the gas turbine engine may further include alubricant cooler.

In yet another refinement, the gas turbine engine may further include amanifold positioned in the main conduit between the lubricant tank andthe flow scheduling valve. The manifold may be connected to the enginecomponent via a side conduit. The manifold may also allow the enginecomponent to receive a flow of lubricant not reduced by the flowscheduling valve.

In accordance with yet another aspect of the disclosure, a method oflubricating a component of a gas turbine engine is disclosed. The methodmay include pumping a lubricant from a lubricant tank through a mainconduit to an engine component by a main pump, calculating a loadcondition of the engine, and limiting the flow of the lubricant to theengine component by a flow scheduling valve. The flow limitation may bebased on the calculated load condition of the engine.

In a refinement, the method may further include directing excesslubricant from the flow scheduling valve though a return conduit to thelubricant tank by way of the flow scheduling valve.

In another refinement, the method may further include measuring anengine combustor pressure and calculating the load on the engine by aprocessor based on the combustor pressure.

In another refinement, the method may further include measuring a fanspeed and calculating the load on the engine by a processor based on thefan speed.

In yet another refinement, the method may further include regulatinglubricant flow from the main pump based on an operating speed of the gasturbine engine.

In yet another refinement, the method may further include redirectinglubricant from the main conduit through a bypass conduit to thelubricant tank.

These and other aspects and features of the present disclosure will bebetter understood in light of the following detailed description whenread in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a gas turbine engine built in accordance withthe present disclosure.

FIG. 2 is a flow diagram of an oil lubrication system built inaccordance with the present disclosure.

FIG. 3 is a flow diagram of an oil lubrication system built inaccordance with the present disclosure and depicting a manifold and afixed flow metering orifice.

FIG. 4 is a flow chart depicting a sample sequence of steps which may beundertaken in accordance with the method of the present disclosure.

It should be understood that the drawings are not necessarily to scaleand that the disclosed embodiments are sometimes illustrateddiagrammatically and in partial views. In certain instances, detailswhich are not necessary for an understanding of this disclosure or whichrender other details difficult to perceive may have been omitted. Itshould be understood, of course, that this disclosure is not limited tothe particular embodiments illustrated herein.

DETAILED DESCRIPTION

Referring now to the drawings and with specific reference to FIG. 1, agas turbine engine 100 is shown. The engine 100 may include a fan 101, acompressor section 102, a combustor 104, and a turbine section 106axially aligned through the engine. The fan 101 may draw in ambient airwhich may then be compressed by the compressor section 102, having a lowand high pressure compressor. The now compressed air may be used in thecombustor 104 as a coolant and as a reactant in the combustion process.The exhaust from the combustion process may exit the combustor 104 andmove through the turbine section 106, causing the turbine section 106 torotate. The turbine section 106, having a high and low pressure turbine,includes a plurality of blades 107 connected to a pair of rotatingshafts 108 and 109 which are concentrically mounted, shaft 109 aroundshaft 108, and are in turn connected to the fan 101 and compressorsection 102. Accordingly, when the turbine section 106 rotates so do thefan 101 and the corresponding compressors of the compressor section 102.As the exhaust exits through the turbine section 106, new ambient air isbrought in and compressed by the fan 101 and the compressor section 102to continue the cycle. While the compressor and turbine sections havebeen described and illustrated as a dual-spool configuration, it shouldbe understood that any configuration of compressors and turbines arepossible, such as, but not limited to, single or triple spoolcompressors or turbines.

Referring now to FIG. 2, the engine 100 may have at least one component110 which needs a lubricant 112, such as an oil, to reduce friction andact as a coolant. The engine component 110 may be an engine gearbox, ashaft bearing, or the rotating shafts 108 and 109, but other enginecomponents are possible. The lubricant 112 may be moved to each enginecomponent 110 through a lubrication system 114.

The lubrication system 114 may include a lubricant tank 116 or sump forstoring the lubricant when not being used by the engine components 110.The lubrication system 114 may have a main pump 118 to draw a constantsupply of lubricant 112 from the lubricant tank 116 through a mainconduit 120. Alternatively, the main pump 118 may draw a varying supplyof lubricant 112. The main pump 118 may be mechanically driven by adrivetrain 119 in mechanical connection with an engine rotor, such asthe compressor section 102 as in FIG. 2, to regulate the flow oflubricant 112 according to an operational speed of the engine 100.Alternatively, the main pump 118 may be regulated by a processor 121 toregulate the flow of lubricant 112 according to an operational speed ofthe engine 100, as in FIG. 3.

The lubrication system 114 may have a main conduit 120 from the mainpump 118 to the engine component 110. The main pump 118 may pump thelubricant 112 through the main conduit 120 to each component 110. A flowscheduling valve 124 is positioned in the main conduit 120 between themain pump 118 and the engine component 110, such as the engine gearbox.

The flow scheduling valve 124 may regulate the flow of lubricant 112directly from the main pump 118 to at least one component 110 such thatall such components 110 may receive a reduced flow of lubricant 112based on a calculated engine load. The engine load may be calculated bythe processor 121 from any suitable parameter such as, but not limitedto, a combustor pressure, a fan speed, an engine horsepower, or thelike. The combustor pressure may be measured by a pressure sensor 125 inthe combustor 104 and the fan speed may be measured by a speed sensor127, for example. As the engine load decreases, the processor 121 maydirect the valve 124 to reduce the flow of lubricant 112 to the enginecomponent 110 by an equivalent percentage.

The lubrication system 114 may also have a scavenge conduit 132 fromeach of the components 110 to the lubricant tank 116 for returning theused lubricant 112 to the lubricant tank 116. At least one scavenge pump134, for pumping lubricant 112 from the components 110 to the lubricanttank 116, may be provided in connection with the scavenge conduit 132.

A lubricant cooler 138 may be positioned in the main conduit 120 or inthe scavenge conduit 132 and may remove heat gained from the enginecomponent 110 from the lubricant 112. The lubricant cooler 138 mayoperate by allowing compressed air or fuel to draw heat from thelubricant 112 through at least one wall of the lubricant cooler 138 orby any other known method. Additionally, a lubricant filter (not shown)and/or a de-aerator (not shown) may also be positioned in the mainconduit 120 or the scavenge conduit 132. The lubricant filter may removeunwanted debris from the lubricant 112, such as coked lubricant, forexample. The de-aerator may separate unwanted air entrained in thelubricant 112 which may have been combined while the lubricant 112 actedon the engine component 110.

The lubrication system 114 described above may be further modified as inFIG. 3. Many elements are similar to the embodiment of FIG. 2, but itwill be noted that a manifold 122 may be positioned between the mainpump 118 and the flow scheduling valve 124 in the main conduit 120. Themanifold may direct a portion of the lubricant 112 through a sideconduit 123 to a first engine component 110. Thus, the engine component110 may receive a flow of lubricant 112 not reduced by the flowscheduling valve 124. Additionally, the flow scheduling valve 124 mayredirect any excess lubricant 112 through a return conduit 126 to thelubricant tank 116. The main conduit 120 between the flow schedulingvalve 124 and the engine component 110 may have a primary conduit 128which accepts the full flow of lubricant 112 exiting from the flowscheduling valve 124. At least one secondary conduit 130 branching fromthe primary conduit 128 may also be provided. Each secondary conduit 130may lead to another engine component 110 and be constructed to receive apre-determined percentage of the total lubricant 112 from the flowscheduling valve 124.

Further in FIG. 3, a fixed flow metering orifice 142 may be positionedin the main conduit 120 between the main pump 118 and the enginecomponents 110. The metering orifice 142 may allow a constant percentageof the lubricant 112 to bypass the entire lubrication system 114, whichmay prevent the lubricant 112 from backing up in the main conduit 120.The metering orifice 142 may allow this excess lubricant 112 to returnto the lubricant tank 116 by a bypass conduit 144. Alternatively, aregulating valve may also allow the lubricant to bypass the lubricationsystem in a similar manner.

In operation, it can therefore be seen that the lubrication system 114is able to lubricate the gas turbine engine 100 according to the methoddepicted in FIG. 4. As depicted, at a first step 200 the main pump 118pumps lubricant 112 from the lubricant tank 116 into the main conduit120. The lubricant is passed through the main conduit 120 to a lubricantcooler to remove excess heat from the lubricant which may have beengained by previously acting on engine components 110, as in a step 202.The cooled lubricant is then passed to the flow scheduling valve 124, asshown by a step 204.

The pressure of the combustor 104 and speed of the fan 101 are then bothmeasured by sensors in the engine 100 as shown by steps 206 and 208,respectively, and a load condition of the engine 100 is calculated fromthe measured values at a step 210. If the load condition is at a maximumas determined by a step 212, all of the lubricant 112 is allowed to passthrough the flow scheduling valve 124 as shown at a step 214. However,if the load condition is less than maximum the lubricant flow is reducedby the valve 124 as at step 216. In such a case, excess lubricant 112 isthen redirected back to the lubricant tank at a step 218, while areduced amount of lubricant 112 is passed through the valve 124. In thisembodiment, all lubricant 112 passing the valve 124 flows through themain conduit 120 to the engine component 110, where the lubricant 112lubricates or removes heat from the component 110. Whether the engine isoperating at a maximum, minimum, or anywhere in between, after passingthrough the flow scheduling valve 124, the used lubricant 112 is pumpedfrom the engine components 110 into a scavenge conduit 134 at a step220. The lubricant 112 is returned through the scavenge conduit 134 tothe lubricant tank 116 at a step 222. Once the lubricant 112 reaches thetank 116 it is once again pumped into the main conduit 120 by the mainpump 118.

INDUSTRIAL APPLICABILITY

From the foregoing, it can be seen that the lubrication system disclosedherein has industrial applicability in a variety of settings such as,but not limited to lubricating and cooling gas turbine engines. Thelubrication system may increase the efficiency of the engine by reducingenergy consumption which would heretofore have been spent on churningexcess lubricant during low load conditions. The lubrication system mayalso increase the efficiency of the engine by reducing the necessarycooling of the lubricant and thus minimizing the size of the lubricantcooler. Minimizing the size of the lubricant cooler may reduce weight ofthe engine and/or air drag, further improving performance.

While the present disclosure has been in reference to a gas turbineengine, one skilled in the art will understand that the teachings hereincan be used in other applications as well. It is therefore intended thatthe scope of the invention not be limited by the embodiments presentedherein as the best mode for carrying out the invention, but that theinvention will include all embodiments falling within the scope of theclaims.

What is claimed is:
 1. A lubrication system for a gas turbine enginehaving a fan and a combustor, the system comprising: a main pump, a flowscheduling valve, and a main conduit fluidly connecting the main pumpand the flow scheduling valve, the main pump moving a lubricant throughthe main conduit from a lubricant tank to the flow scheduling valve, afirst engine component fluidly connected by a first primary conduit tothe flow scheduling valve, a second engine component fluidly connectedby a second primary conduit to the flow scheduling valve, wherein themain pump moves the lubricant to the flow scheduling valve; and aprocessor connected to the flow scheduling valve and at least one sensorthat provides at least one measured value, the processor of configuredto; receive the at least one measured value from the at least onesensor, calculate an engine load based on the at least one measuredvalue, selectively control flow scheduling valve to proportionallyreduce flow of the lubricant to both the first engine component and thesecond engine component and the second engine component in response todetecting a reduced value of the calculated engine load, and wherein theat least one sensor includes one or both of a pressure sensor providinga measured pressure of the combustor and a speed sensor providing ameasured speed of the fan, and wherein the at least one measured valueincludes the corresponding one or both of measured pressure and measuredspeed.
 2. The lubrication system of claim 1, further comprising alubricant cooler connected to the main conduit.
 3. The lubricationsystem of claim 2, wherein the lubricant cooler is positioned betweenthe main pump and the flow scheduling valve.
 4. The lubrication systemof claim 1, further comprising a fixed flow metering orifice allowingthe lubricant to bypass the first engine component and the second enginecomponent via a bypass conduit and to return to the lubricant tank. 5.The lubrication system of claim 1, further comprising a manifoldpositioned in the main conduit between the main pump and the flowscheduling valve, the manifold being connected to a third enginecomponent via a side conduit to allow the engine component to receive aportion of the lubricant not reduced by the flow scheduling valve. 6.The lubrication system of claim 1 further comprising a first scavengeconduit fluidly connecting the first engine component and the secondengine component to each other and to the lubricant tank.
 7. Thelubricant system of claim 1, wherein the at least one sensor includesboth of the pressure sensor providing the measured pressure of thecombustor and the speed sensor providing the measured speed of the fan,and wherein the at least one measured value includes the correspondingboth of measured pressure and measured speed.
 8. A gas turbine enginecomprising: a fan and a combustor, and a lubrication system, thelubrication system comprising: a lubrication tank; a main conduit influid communication with the lubrication tank; a main pump, a flowscheduling valve, and the main conduit fluidly connecting the main pumpand the flow scheduling valve, the main pump moving a lubricant throughthe main conduit from the lubricant tank to the a flow scheduling valve,a first engine component fluidly connected by a first primary conduit tothe flow scheduling valve, a second engine component fluidly connectedby a second primary conduit to the flow scheduling valve; and aprocessor connected to the flow scheduling valve and at least one sensorthat provides at least one measured value, the processor configured to;receive the at least one measured value from the at least one sensor,calculate an engine load based on the at least one measured value,selectively control the flow scheduling valve to proportionally reduceflow of the lubricant to both the first engine component and the secondengine component in response to detecting a reduced value of thecalculated engine load, and wherein the at least one sensor includes oneor both of a pressure sensor providing a measured pressure of thecombustor and a speed sensor providing a measured speed of the fan, andwherein the at least one measured value includes the corresponding oneor both of measured pressure and measured speed.
 9. The gas turbineengine of claim 7, wherein the main pump is driven by a drivetrain. 10.The gas turbine engine of claim 7, further comprising a lubricant coolerconnected to the main conduit.
 11. The gas turbine engine of claim 7,further comprising a manifold positioned in the main conduit between thelubricant tank and the flow scheduling valve and connected to a thirdengine component via a side conduit, the manifold allowing the thirdengine component to receive a portion of the lubricant not reduced bythe flow scheduling valve.
 12. The gas turbine engine of claim 7,further comprising a first scavenge conduit fluidly connecting the firstengine component and the second engine component to each other and tothe lubricant tank.
 13. The gas turbine engine of claim 7, wherein theat least one sensor includes both of the pressure sensor providing themeasured pressure of the combustor and the speed sensor providing themeasured speed of the fan, and wherein the at least one measured valueincludes the corresponding both of measured pressure and measured speed.14. A method of lubricating a first component and a second component ofa gas turbine engine, the gas turbine engine having a fan and acombustor, comprising: moving a lubricant through a main conduit from alubricant tank to a flow scheduling valve by a main pump, the mainconduit fluidly connecting the main pump and the flow scheduling valve,fluidly connecting the first component to the flow scheduling valve witha first primary conduit, fluidly connecting the second component to theflow scheduling valve with a second primary conduit, moving thelubricant to the flow scheduling valve with the main pump, and providingat least one measured value from at least one sensor to a processor, theprocessor connected to the flow scheduling valve and the at least onesensor, calculating an engine load with the processor based on the atleast one measured value, regulating the main pump with the processor toselectively control the moving of the lubricant through the main conduitfrom the lubricant tank to the flow scheduling valve according to anoperational speed of the gas turbine engine, selectively controlling theflow scheduling valve with the processor to proportionally reduce flowof the lubricant to both the fires component and the second component inresponse to detecting a reduced value of the calculated engine load withthe processor, and wherein the at least one sensor includes one or bothof a pressure sensor providing a measured pressure of the combustor anda speed sensor providing a measured speed of the fan, and wherein the atleast one measured value includes the corresponding one or both ofmeasured pressure and measured speed.
 15. The method of claim 14,further comprising directing an excess portion of the lubricant througha return conduit to the lubricant tank.
 16. The method of claim 14,further comprising redirecting a portion of the lubricant from the mainconduit through a bypass conduit to the lubricant tank.
 17. The methodof claim 14, wherein the at least one sensor includes both of thepressure sensor providing the measured pressure of the combustor and thespeed sensor providing the measured speed of the fan, and wherein the atleast one measured value includes the corresponding both of measuredpressure and measured speed.